Arrhythmias

Question 1

What are the different types of arrhythmias

Answer 1

Tachy arrhythmias - fast

Brady arrhythmias - slow

Question 2

Give examples of tachy arrhythmias

Answer 2

Atrial fibrillation

Ventricular tachycardia

Question 3

Give examples of Brady arrhythmias

Answer 3

Heart block

Drug induced - Beta blockers, digoxin

Question 4

What is the most common pulse in bradyarrhythmias

Answer 4

50bpm

Question 5

Describe heart block

Answer 5

Slow or no conduction through the AV node to ventricles of impulse from SA node

Question 6

What can be seen on an ECG of a patient with heart block

Answer 6

Prolonged PQ interval

Question 7

What are the different levels of heart block and how are they classified

Answer 7

1st degree, 2nd degree
3rd degree - complete heart block as no impulse is passed to the ventricles
Classified by the length of signal delay

Question 8

What is the correlation between heart rate and risk of arrhythmia

Answer 8

As heart rate increases, the risk of arrhythmia increases

Question 9

How does ventricular tachycardia relate to ventricular fibrillation

Answer 9

VT is a precursor for VF

Question 10

Describe the ECG of a patient with 3rd degree heart block

Answer 10

Regular P intervals but they are not necessarily tied to QRS complexes

Question 11

Describe how atrial fibrillation appears on an ECG

Answer 11

Electrical activity arises throughout the atria rather than just the SA node
Narrow QRS, waves aren’t a fixed interval apart
No p waves as disorganised atrial activity
Irregular pulse - termed irregularly irregular

Question 12

How does atrial fibrillation affect heart rate

Answer 12

Rapid atrial impulses conducted to ventricles giving high heart rate

Question 13

How does ventricular tachycardia appear on en ECG

Answer 13

Broad QRS complex

Question 14

Why is ventricular tachycardia particularly dangerous

Answer 14

Can lead to ventricular fibrillation and death

Question 15

What abnormality occurs in the cardiac conduction system in AF

Answer 15

Many P waves are trying to get through to the ventricle through the AV node, but the AV node is only allowing a small number through

Question 16

What abnormality in the cardiac conduction system causes VT

Answer 16

The time taken to activate the ventricular muscle is longer and as soon as it is finished, it starts again
This leads to electrical activity becoming uncoordinated
No coordinated muscle activity to allow the heart to work as a pump

Question 17

What are cardiac pacemakers used to treat

Answer 17

Bradyarrhythmias

Question 18

What is the purpose of a cardiac pacemaker

Answer 18

To keep the heart rate at a minimum level

Question 19

How is a cardiac pacemaker fitted

Answer 19

Box fitted in chest wall on left side
Wires are passed through the vena cava, through the atria, one placed within the atrial wall another placed in the ventricle to trigger ventricular contraction

Question 20

How do cardiac pacemakers work

Answer 20

Stimulate heart action by pacing atria and ventricles in sequence

Question 21

Which dental equipment should be avoided with patients with pacemakers and why

Answer 21

Induction scalers as they generate a strong EM field

Question 22

What has a theoretical risk of shutting a cardiac pacemaker down

Answer 22

Electrical fields such as an MRI or diathermy

Question 23

When is an implanted defibrillator useful

Answer 23

Useful for patients with unstable cardiac rhythms

Question 24

Where is an implanted defibrillator placed

Answer 24

Subcutaneously on the right side

Question 25

How does an implanted defibrillator work

Answer 25

Has wires passing to the heart and will look for evidence of VF Where there is, it will use a low energy pulse to coordinate the electrical activity and shock the heart out to VF very rapidly

Question 26

What cardiac rhythms should I be able to recognise

Answer 26

Sinus rhythm Asystole Ventricular Fibrillation

Question 27

In what cardiac arrhythmias do i need to know their clinical presentations

Answer 27

Atrial fibrillation | MI

Question 28

What does the P wave correlate to in sinus rhythm

Answer 28

Atrial depolarisation

Question 29

What does the QRS complex correlate to in sinus rhythm

Answer 29

Ventricular depolarisation

Question 30

What does the T wave correlate to in sinus rhythm

Answer 30

Ventricular repolarisation

Question 31

Why is the P wave in sinus rhythm small

Answer 31

There isn’t much muscle in the atria

Question 32

Why is the QRS complex in sinus rhythm narrow and large

Answer 32

The bundle of His carries the electrical activity to the whole ventricle muscle very rapidly so the muscle contracts in a single unit creating a large electrical signal

Question 33

How is ventricular fibrillation treated

Answer 33

Defibrillation

Question 34

Describe ventricular fibrillation

Answer 34

No cardiac output Electrical heart activity but disorganised Muscle fibres contracting in ventricles at random so there is no emptying of ventricles

Question 35

What can cause ventricular fibrillation

Answer 35

Heart attack Electrocution Long QT syndrome - can be drug induced Wolf-Parkinson-White syndrome

Question 36

Describe asystole

Answer 36

No cardiac output No electrical activity Defibrillation not possible Low chance of survival

Question 37

How can a patient in asystole be treated

Answer 37

Treated with adrenaline to try and produce some electrical activity in the heart so that a defibrillator can be used - tends not to be successful